A slide fastener, sometimes commonly referred to as a zipper, generally comprises a pair of slide fastener halves which have respective coupling elements formed along edges of a support such as a tape or the like, to which the coupling elements can be affixed or on which the coupling elements can be formed so, upon movement of a slider along the coupling elements in one direction, respective coupling heads of one coupling element can be pressed between the coupling heads of the other coupling element and vice versa so that the coupling heads are interdigitated, i.e. each coupling head lies in a gap between coupling heads of the other coupling element and is retained against withdrawal from the gap by the head configuration which can include lateral protrusions reaching behind lateral protrusions of the retained head.
Upon movement of the slider in the opposite direction, the coupling elements are urged apart to disengage the heads of the two coupling elements.
The coupling elements may be respective rows of individual coupling members formed with the heads and clamped upon or molded onto a support tape. Alternatively, the coupling heads may be meanders of a continuous synthetic resin monofilament molded with the heads at respective bends of the loops forming the meanders.
In another construction the coupling elements may be coils with the coupling heads formed on or by respective turns of the coil of synthetic resin monofilament.
The attachment of the coupling element to the support tape may be effected in the manner described or by stitching the coupling element onto the tape or weaving or knitting the coupling element onto the tape, or even by passing the heads of the coupling elements through openings formed in the tape.
A pair of slide fastener halves can constitute, with the respective slider, a slide fastener stringer and the slide fastener stringer may form a separable slide fastener or a nonseparable slide fastener. A separable slide fastener has end stop members at one end of the stringer and respective opposite end stop members one of which acts as a stop for the slider and the other of which forms a plug that can be inserted through the slider into the end stop member of the other coupling element to join the slide-fastener halves for closure of the slide fastener upon movement of the slider away from these end stop members.
In a nonseparable slider fastener, the two ends of the stringer are held together by respective end stop-members.
The slider itself can comprise a slider body which generally has the configuration of a pair of shields bridged by a core or heart piece, the latter serving to urge the coupling elements apart when the slider is moved in an opening direction along the coupling elements. The shields straddle the coupling elements and form guides for the latter which press the coupling elements together when the slider is moved in the closing direction.
A pivotal handle may be provided on an upper shield so as to be gripped between fingers of the user for manipulating the slider.
Sliders of this type also can include a spring member having a locking tooth which passes through the upper shield and engages between the coupling heads of the stringer when the handle is in one position to lock the slider against movement. The handle is provided with an eccentric which is effective to withdraw the tooth or pawl from its engagement with the coupling elements when the handle is swung outward to allow movement of the slider along the coupling elements. The spring member is generally retained in the slider body by formations which can engage over edges of the spring member.
In a conventional construction of this type (see German Patent Document DE-OS No. 25 04 811), the fastening elements of the spring member include, in a projection on the slide fastener plane, lateral portions which together with the centrally disposed spring tongue form the tines of a fork projecting from the body. The spring tongue thus effectively functions as a leaf spring supported at one side. As a result, the spring characteristic of the member has generally a low spring force and indeed a spring force which in the locked position is the smallest. This has resulted in attempts to provide inwardly extending bracing members on the support urging the spring element upon the slide fastener body as shown in that patent document.
While this increases the spring force, nevertheless a sufficient spring force requires relatively thick spring plates which may be disadvantageous because they must be held by a proportionally more massive structure and tend to apply increased stress to the slider body, raising the danger of breakage or deformation.